238 



COMPARATIVE ANATOMY. 



pared with the epithelial cells, E l E l , of the intestine of a lower 

 Vertebrate, in Fig. 194, A, where they are shown putting out 



BH M 1 Z L S 



a 



FIG. 194. A, SEMIDIAGRAMMATIC TRANSVERSE SECTION OF A PORTION OF THE 

 WALL OF THE INTESTINE. (Combined from the condition seen in both lower 

 and higher Vertebrates.) 



The connective-tissue layer and epithelium are designedly drawn much too large 

 as compared with the outer coats. To the left of the figure would be the 

 body-cavity ; to the right, the alimentary cavity. 



P, peritoneal investment of the gut ; M, longitudinal muscular layer ; M l , circular 

 muscular layer ; Z, connective-tissue layer ; S, mucous membrane, which is 

 raised to form villi at Zo ; G, G, vessels, the larger trunks running between the 

 peritoneum and the muscular layer : the finer vessels branch out into the inter- 

 mediate layer ; these surround the masses of lymph-cells, LL, as well as the 

 glands, and send fine loops into the villi (at Cf 1 ) ; DD, apertures of the glands ; 

 E, E, epithelial cells of the mucous membrane, with their striated border, from 

 which at E 1 amreboid processes are extruded : in Fig. B, a, b, these cells are 

 drawn to a much larger scale (Sa, striated border) ; Ly, scattered lymph-cells 

 in the intermediate layer ; Z 1 , Z 3 , lymph-cells in the act of passing through 

 the mucous membrane ; at Z 2 , several have already passed into the alimentary 

 cavity, and are beginning to ingest the contained nutritive particles by means 

 of their amoeboid processes ; LL, masses of lymph-cells (solitary follicles) ; 

 Lym, lymph -vessels in the villi. 



amoeboid processes, and in Fig. 194, B, where the cells a, I, are 

 shown drawn to a larger scale. Besides these absorptive epithelial 



